Plug gauge



Jan. 3, 1950 E. w, DOWER 2,493,233

PLUG GAUGE Filed Dec. 27, 1944 Edward M. Bower Guam/Ms Patented Jan. 3, 195@ NITED STATES t r orrlcE PLUG GAUGE Edward W. Bower, Elgin, Ill., assigner Ito Elgin National Watch Company, Elgin, Ill., a .carporaiion `ci Illinois 3 Claims.

This invention relates to a plug gage, which can be easily and accurately made, vand which is not subject to breakage .or te tendency to deorm the article to be gaged or itself undergo deformation cr major wear.

Plug gages are employed by inserting the gage member into. a hole whose size and laccuracy is to be determined by a linear movement: and a reverse linear movement is used to withdraw the gage. Particularly with small holes, `it is difcult for the operator to assure .that the gage will -enter and leave truly rin the line -of the axis of the .aperture, as cocking easily occurs, wherewith severe strains are produced upon the gage as well as upon the article, so that breakage may occur, or rapid wear be induced and deformation occasioned. It is obviously `desirable to make the plugs of highly wear-resistant materials but such materials are brittle and cannot endure heavy bending strains, particularly as `these strains are determined by the operators strength and skill and not by the size of the plug.

Further, it is difficult to make and suppcrt the gages of small sizes, say from 0.2 50 inch d ownward. This is particularly `true since small gages may be designed to work to such close telerances that binding occurs, and hence when the gage is made of uniform cross-section Vthe necessary length incurs a corresponding probability of breakage. When it is sought to make the gages of other than regular .cross-seetQn., difficulty is encountered. preparing them accurately to the calibrated section.

This invention is concerned with a gage having a mounting for the plug itself, wherewith the plug is supported for introduction and removal and the handle member permits flexibility so that pulls or pushes which are not in line with the axis do not cause breakage, and so that the handle may be given a force couple in an axial plane without over-straining the plug itself.

This assembly is particularly valuable with plugs made of the highly wear-resistant refractories, as it permits forming the plug of uniform diameter, of binding it to the handle member against separation, and of assuring the plug against breakage even under severe conditions of employment.

An illustrative form of practicing the invention is shown in the accompanying drawings:

Figure 1 is a side elevation of a double-ended is of rigid material, illustratively being 0f ce1-jun,-I which isr a highly wear-resistant lfeflnCOry ci" nxed `dimensions and physical properties, being 'k own in various forms as. sapphire, `ruby, practice, it has been found that syn# f ic sapphire rods may be ground and polished r entire lengths to give a uniferm diameter nf erossfsection, and ,by controlling .the abra.-` s-ive and polishing operations., with use of fine hide pewder, 4chemical polishing vor flame `the plug can :be brought accurately :to l dimension even .when the tolerances a ia eter of @.luinch 4and the other plug [a eter cf 9.13% .inch so that .the double-.ended e is capable of determining whether the hole lies Vbetween these two .extremes of dimension. as small as @.649 inchin diameter and hav-v ing an exposed length of 0.120 inch, or smaller, can be thus made.'

In the illustrative form of practice, the inner end of the plug, `being 4that spaced Afrom the gag. ing end, provided with a collar Yll formed of a .material which bonds directly to vsapphire .and like corundumpieces.

This assembly is then surrotmded by a `handle l2 which preferably is of angular section such/as a -hexagon or Octagon. While various `types of rubber may be employed for liexibility, vit is pre-Y ferred to employ a syntheticrubber because -of-its freedom from deterioration when in contact-with oil, etc. In gages which have been made, a synthetic rubber made by a polymerizing condensation of chlorobutadiene, known as neoprene, has been employed in a hardness of to 80 Duro units. That is, the material has the properties of a soft rubber (ASTM test designation D-676- 42T). The handle l2 be formed as a separate unit having bores into which the gage assemblies are inserted. Preferably, the ends of the handle are reduced in diameter and of circular section, and have a screw thread molded thereon.

Among the bonding materials which have been found useful are the synthetic plastic known as nylon (for example nylon D), ester gum, shellac, and sealing wax, of which sealing wax is presently preferred. The preformed plug is dipped into the liquid bonding agent, for example in the form of a solution, and then inserted into the bore provided in the handle pieces. When the solution of the bonding agent in a solvent has been induced by heat, it is preferred to heat the assembly to effect bonding to the handle. When sealing Wax is employed, it is preferred to melt the sealing wax by heat, dip the inner end of the plug into the wax for the distance by which the plug is to be introduced: a collar of wax is permitted to form by cooling and again dipping for the axial length of the collar, this redipping being accomplished until the desired outer diameter is obtained. The cold plug with its collar and coating is then inserted into the handle, and heat is applied to the assembly to cause remelting of the wax and its bonding to the material of the handle for the entire embedded length as indicated by the lm I4 in Figure 2. With small sizes of gages, it is feasible to omit the collar formation and therewith the recess at the inner end of the handle bore.

It is prferred to complete the gage by employing a ferrule formed as a nut I3 which may be of metal or other form-retaining material capable of resisting expansion of diameter. It is preferred to form threads on its inner surface, so that the ferrule I3 may be threaded upon the tapered reduced end of the gage handle (see Fig. 2) and thus tightly engage and hold the rubber under compression, and also provide a means for exerting a withdrawing tension upon the gage during use. The eiect of the ferrule is to compel the material at the end of the handle to move with the gage plug as the latter shifts from coaxial position, and thus prevent tension strains across the bonding interfaces. When a collar l l is used, it will also be noted that the ferrule acts mechanically to prevent disengagement so long as the collar remains bonded to the plug. When the ferrule is larger than the body of the handle, as illustrated, it is preferred to have at least one ferrule formed with flat peripheral faces to prevent rolling.

In use, the gage can be held by the hand at the end opposite the gage plug I which is to be employed, and this plug is then introduced to the hole to be gaged. The exibility of the handle permits the plug to conform to the true axis of the hole and hence the introduction can be performed without accurately aligning the gage. In withdrawing the gage, it will be noted that any rocking performed by the operator is relieved by the flexibility in the handle, so that the gage is not broken within the hole.

It is to be understood that the invention can be employed in many ways other than in the i1- lustrative way, Within the scope of the appended claims.

What is claimed is:

1. A gage comprising a rigid plug of uniform calibrated cross-section, a separate collar having a bonding connection to said plug at a point spaced from the gaging end of said plug, and a exible rubber handle surrounding and closely conforming to said collar and the non-gaging part of the plug and engaging said collar whereby pulls on the handle are transmitted to the plug.

2. A gage comprising a corundum plug of uniform calibrated cross-section, a collar having a bonding connection to said plug adjacent the non-gaging end, a flexible rubber handle surrounding and engaging said collar whereby pulls on the handle are transmitted to the plug, said handle having a reduced end where it surrounds said collar and the non-gaging part of said plug, and a form-retaining ferrule tightly engaged with said reduced end and effective to hold the material thereof closely pressed upon a part of the plug outward of said collar.

3, A gage comprising a corundum plug o uniform calibrated cross-section, a exible rubber handle having a reduced threaded end surrounding a part of said plug, a layer of bonding material adherent to the plug and to the handle and effective to secure the embedded portion of the plug to the handle, and a form-retaining ferrule with an integral thread engaged with the handle thread and in compressing relationship with the material of the handle end, said ferrule being of larger external diameter than the body of said handle and having at peripheral faces.

EDWARD W. DOWER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 264,527 Haley Sept. 19, 1882 264,798 Tyler Sept. 19, 1882 2,043,442 McNeil June 9, 1936 2,173,942 Hiatt Sept. 26, 1939 2,197,756 Brescka et al. Apr. 23, 1940 2,345,749 Hohwart Apr. 6, 1944 2,345,750 Hohwart Apr. 6, 1944 OTHER REFERENCES American Mach., June 8, 1944, page 132. 

